Signal relay system



Nov. 10, 1936. A. P. J. BOUDREAU SIGNAL RELAY SYSTEM Filed July l,v 1932 FIG. I

FIGSZ T N E R R U C T U P T U 0 m T C E T F- D 33 ems CURRENT INII/ENTOR A. P. J. BOUDREAU W ATTORNEY Patented Nov. 10, 1936 UNITED STATES PATENT OFFICE SIGNAL RELAY SYSTEM New York Application July 1, 1932, Serial No. 620,482

7 Claims.

This invention relates to vacuum tube operated relays, particularly to relays operated by a vacuum tube detector responding to signal modulations of a received carrier wave.

The principal object of this invention is to provide for supplying the current for both windings of a polar relay from a single source, and means to maintain the ratio of the flux from both windings substantially uniform when the current for one winding is supplied through a vacuum tube and when the potential of the current source is subject to voltage fluctuations.

Another object of this invention is to provide an arrangement whereby polar relays may be eil'ectively operated by current supplied through a vacuum tube detector under conditions in which the potential of the space current supplied to the detector is subject to fluctuation and which would ordinarily cause an unbalance of the operating condition of the relay.

A further object of this invention is to supply a balancing or biasing current to said relay which varies in accordance with the variation of space current passed by said detector tube due to voltage fluctuations in the space current supply.

When telegraph signals or the like are transmitted by means of a modulated carrier wave, the signals at the receiving end are demodulated or detected by means of the well known vacuum tube detector arrangement. The output of a detector is in the form of a pulsating direct current wave of an amplitude corresponding to the modulations of the carrier wave. For telegraph signals the peak of this current wave ordinarily represents a marking current pulse, while the other limit of the wave represents a spacing pulse. This form of signal coming from a detector can be adapted to effectively operate a polar relay when certain conditions are maintained.

In order to so operate a polar relay one of the windings is energized by pulsating direct current to produce the operating flux in a relay and an opposing biasing or counterbalancing flux having a value about equal to the average or mean value of the operating flux is supplied through another winding of the relay. So long as this condition is maintained, the tongue of the relay is held in engagement with one or the other of the respective contacts for a period substantially equal to that representing the respective marking and spacing signals. On the other hand, if this steady balance is not maintained between the fluxes the tongue of the relay will be moved from one contact to the other earlier in the signal cycle as it swings in one direction and later as it swings in the other direction producing an unequal response in the relay.

It is a known characteristic of vacuum tubes in general that the space current passed by the tube changes with a change of the current potential supplied to the electrodes of the tube. It is further known that the characteristic of this change of current does not follow the law of a common ohmic resistance. On the other hand, space current passed by a tube instead of chang- 10 ing in direct ratio as it would through a fixed ohmic resistance changes as some power of the potential across the tube. This is because the ohmic resistance of the tube varies with a change in the potential of the space current.

Under conditions ordinarily encountered in telegraph service the current supplied to vacuum tubes would come from a common station or ofllce battery. This same battery usually supplies current for various other purposes at the station or office. In certain cases a generator is employed in place of a battery for supplying current. This would likewise be subject to varying load conditions. As a result the available potential of the vacuum tube current supply in either case will be subject to fluctuation.

Attempts have been made to solve the problem arising in connection with vacuum tube operated polar relays, by introducing an ohmic resistance in the circuit supplying current to the bias winding in an effort to counter-balance'the ohmic resistance of the detector tube which supplies the current to the other winding. Obviously, since the resistance of the vacuum tube detector does not remain uniform but changes with a change in potential of the space current source, the fluxes through said relay would become unbalanced when the potential of the source dropped off due to addition load placed thereon. 40

According to this invention this diificulty is overcome by supplying the current to the biasing winding of the relay through one or more supplementary or auxiliary vacuum tubes having a resistance characteristic which changes substantially in the same manner as the resistance characteristic of the detector. The supplementary tubes thus employed may be the tube or tubes in a preamplifier in the receiver or they might be tubes merely maintained in operation by current 5 supplied from the common source and serving only as a controlling resistance in the circuit of the biased winding of the relay.

For a more complete description of this invention reference may be had to the accompanying 5 drawing. together with the following description, in which:

Fig. 1 represents a diagrammatic view of one form oi the signal receiver embodying this invention, and

Fig. 2 a diagrammatic illustration oi the conditions obtained with a receiver operated in accordance with this invention.

Reierringto the drawing, Fig. 1 represents a diagrammatic circuit oi a signal receiver. The receiver embodies a polar relay l arranged to be actuated by a vacuum tube detector II which, in turn produces a signal wave in response to modulations in a received carrier wave. The detector may be preceded by a carrier amplifier embodying one or more tubes. In the illustration the amplifier embodies tubes l2 and II. The polar relay is provided with a pair of windings i4 and II. The winding M is connected in circuit with the anode I6 01' the detector tube. The circuit includes a portion of the potentiometer I! which is bridged across a source of current i8. This source of current may be a battery or a generator and is ordinarily the source which supplies current to various other apparatus. The space current circuit for the'detector is completed through the detector cathode l9 and ground.

As the detector is actuated through its grid 20 by the incoming carrier wave, it detects or rectiiies this wave in a well known manner to produce a pulsating output corresponding to the modulations of the carrier wave. This pulsating current passing through the winding M of the polar relay supplies the actuating current for the relay. For the purpose of analysis the output of a detector may be resolved into a direct component equal to its mean output value and an alternating current component of a value equal to the amplitude of the signal pulsations. It is well known that a pulsating unidirectional current may be employed to eflectively operate a polar relay if the flux due to the direct current component is counterbalanced by a biasing flux in the opposite direction. This leaves only the alternating component eiiective to actuate the tongue or armature 2| of the relay. The biasing flux may be supplied by passing a current through winding ii in the proper direction. The relay comprises in addition to the windings i4 and I and the tongue or armature 2l, a pair of contacts 22 and 23 upon which plus and minus battery, respectively, is imposed. From the tongue 2| the current passes through a receiver for recorder R". The current through the winding I5 is supplied from the same potential source II, but is arranged to pass through the winding ii oi the relay in a direction to produce a flux opposing that produced by the direct current component of the signal current through the winding It.

In order to provide for proper operation under fluctuating conditions, the amount of current through the winding I! must be at all times of a value required to produce a counter flux substantially equivalent to the average flux produced by the direct current component of the signal current through the winding ll.

In other words a signal wave at its midpoint should be just balanced by the current through the winding i5 so that, momentarily, the tongue 2i will have no force acting thereon. As the signal wave moves above or below the midpoint or mean value the balance between the two fluxes is disturbed and the tongue 2| moves toward one or the other of the contacts. The tongue remains upon the contact until the signal wave reaches its midpoint traveling in the opposite direction. As it passes the midpoint, the tongue is swung to the other contact. From this it'will be seen that when the counter balancing or biasing flux oi the winding II is adjusted to neutralize the signal wave at the midpoint, the tongue is in engagement with the proper contact for a time corresponding to the length of a signal pulse as represented by the upper or lower half of the wave. On the other hand, ii for any reason the biasing flux does not maintain its balance, the reproduced signals will be distorted due to the fact that the tongue oi the relay is moved against one of the contacts at an earlier point in the signal cycle as the signal swings in one direction and at a later point in the cycle as it swings in the opposite direction, thus lengthening one of the signals while shortening the other.

In order to control the amount oi current passing through the winding IS, the circuit is completed through the amplifier tubes l2 and II. Included in this circuit is an inductance 24 and a bi-pass condenser 25 which filters out the alternating current component 01' the output of the amplifier tubes. In this manner a substantially direct current is passed through the winding II. In this circuit it will be seen that the principal resistance is the resistance oi the tubes i2 and ii. In other words, the resistance oi the tubes l2 and I3 comprise the controlling resistance 0! the circuit. As already observed, the ohmic resistance oi the detector tube ll controls the amount of current passed through the winding ll. Also that this resistance varies as the potential oi the space current source varies, not in direct proportion thereto but at some other ratio determined by the characteristic oi the tube. In the circuit of the other winding ii of the relay a similar varying controlling resistance, due to the tubes l2 and i3 determines the amount of current passing through that circuit at the various potentials of the current source ll. It will be seen, therefore, that the same type of controlling resistance is present in both of the circuits providing current for the respective windings oi the polar relay and when the direct current component 0! the output or the detector tube drops 01! due to a decrease in the potential of the current source l8, the amount of current passing through the bias winding IQ of the relay will drop ofl in substantially the same proportion. It should be observed in this connection that a common blocking resistance in the circuit of the biasing winding of the relay would cause the current through the winding to drop oil as the potential 01 the source decreases but that such drop in the amount of current following Ohms law would be in direct proportion to the decrease in the source potential. This. however, would not maintain the proper balance or the counteraction oi the biasing winding described above. In other words, the flux due to the direct current component of the detector output and that due to the biasing winding would not remain the same for the lower potentials of the current source. However, when the same type of controlling resistance is present in both of the circuits the balance will be substantially maintained at all times.

In order to enable the proper balance to he arrived at, an adjustable shunt resistance 26 is provided in one leg of the circuit through the winding l5. This is connected in the circuit by a double throw switch 21. one position, the resistance may be connected in With this switch in parallel with the winding ll so as to pass a less amount of current through the winding than is provided by the space current'output of the tubes l2 and I3. When the switch is in the other position, the variable resistance is connected with ground enabling current to be shunted to the ground after it has passed through the winding II, in this manner, adding to the amount of current supplied by the tubes l2 and i3. This arrangement enables a substantially accurate balance to be obtained under widely different conditions.

Referring to Fig. 2, the action of a detector output circuit and the controlling circuit. is illustrated. The sine curve 3| illustrates the 10v! frequency output of the detector generated by the action of the modulations in the carrier wave. The dash line 32 represents the direct current component of the detector output or the mean value of the curve 3|. The illustration is intended to show what happens as the potential of the space current source It (Fig. 1) drops on. When this drops off the average amount of current passed by the detector also drops oi! as indicated by the slope of the line 32. In order to maintain the proper operating balance of fluxes in the polar relay, a biasing current of an opposing potential substantially equivalent to the mean value 32 of the signal current is passed through the biasing winding of the relay. Such a biasing current is illustrated by the line 33. When the proper adjustments are made, the biasing current 33 would drop off in substantially the same proportion as the direct current component of the signal current 32. When this condition obtains the value of the flux due to the biasing current and that due to the direct current component of the signal current will remain substantially equal at all times and the tongue of the relay will respond in the same manner to the respective upper and lower portions of a signal irrespective of the fluctuations in the space current source for the detector tube.

It is to be understood that the lines 32 and 33 are not intended to represent an actual current change but are intended solely to represent the relation between the two currents for an assumed change.

Although this invention has been described in its preferred form as being applied to polar relays operated from a detector tube signal repeating arrangement, it may be applied with equal facility to any type of vacuum tube operated repeater employed to repeat signal pulses. The same type of problem is involved when vacuum tubes are employed in any type of signal repeater or amplifier where the potential of the space current source is subject to fluctuation. It is obvious to persons skilled in the art that the principles of this invention may be readily applied to any type of vacuum tube amplifier or repeater without departing from the spirit of the invention and such application of the principles is contemplated.

From the foregoing description, it will be observed that an arrangement has been provided whereby a polar relay which has been adjusted in any desired effective manner to operate from the output of a detector tube will be maintained in adjustment irrespective of potential fluctuations in the source of current supplied to the detector tube. This is a highly advantageous result because heretofore the reception of telegraphic signals transmitted by carrier wave has not been as satisfactorily accomplished as signals transmitted by the ordinary code pulses. This was due mainly to the inability of maintaining the proper adjustment or relation between the output of the carrier wave detector and the receiving relay which must necessarily be connected therewith to transmute the signals into a form readily usable as telegraph signals. It will further be observed that the results have been accomplished by employing apparatus which is relatively simple and effective.

"Although this invention has been shown in but one form, it will be apparent to those skilled in the art that it is not so limited but is susceptible to various changes and modifications without departing from the spirit thereof and it is desired, therefore, that only such limitations shall be placed thereon as is imposed by the prior art or as set. forth in the appended claims.

What I claim is:

1. A signal receiving circuit embodying a vacuum tube detector, a polar relay to be operated by the detector, said relay having two windings, a vacuum tube amplifier ahead of the detector, a source of space current for said detector and amplifier, circuit connections such that one winding of said relay is energized by current supplied from said source through said detector, and the other winding is energized by current supplied from said source through the tubes of said amplifier and filter means between said amplifier and said other winding to filter out current fluctuations which the amplifier tends to introduce.

2. A signal receiver embodying a polar relay having a bias winding and an operating winding, a detector arranged to actuate said relay, a current source for supplying space current to the ;detector, saiddetector having an ohmic resistance characteristic which changes a definite amount with a change of the potential of the space current supplied to said detector, and circuit connections such that the operating winding of said relay is energized by pulses of detected current supplied through said detector, and means to energize the bias winding by a substantially steady current which varies substantially in the same proportions as the average value of the detected current supplied through said detector.

3. In a signal repeater embodying electronic tube repeating means, a current source for said repeater subject to potential fluctuation, a polar relay arranged to be operated thereby, said relay having two windings, circuit connections for energizing one of said windings by the space current from a tube of the repeating means in a relatively unfiltered form, circuit connections having filter means included therein for energizing the other winding of said relay by the space current of a tube of the repeating means in a relatively steady-form, and a variable resistance connected in shunt to the circuit of the second winding beyond the current source for providing an adjustable current path to shunt circuit through said winding in excess of the space current required by the tube of said circuit.

4. In signal repeating means embodying an electronic tube repeater, embodying a series of. two or more tubes connected in cascade, a current source for said repeater subject to potential fluctuation, a polar relay arranged to be operated thereby, said relay having an actuating winding and a bias winding, circuit connections for energizing the actuating winding of said relay by the space current from the output tube oi. said repeater in a relatively unfiltered form, circuit connections having illter means included therein for energizing the bias winding of said relay by the space current of one or more of the other tubes of said repeater in a relatively steady current form, and a variable resistance connected in shunt to the circuit .01 the second winding beyond the current source for providing an adjustable circuit path to shunt current through said winding in excess of the space current required by said other tubes.

5. In signal repeating means embodying an electronic tube repeater having a series of two or more tubes connected in cascade. a space current source for said tubes subject to potential fluctuation, a polar relay arranged to be operated by said repeater, said relay having an actuating winding and a bias winding, circuit connections for energizing ,the actuating winding of said relay by the space current from the output tube of said repeater in relatively unfiltered form, circuit connections for energizing the bias winding of said relay by the space current of one or more 01' the other tubes of said repeater, filter means included in said circuit connections for feeding the current to said winding in a relatively steady form, and a variable shunt resistance connected to a point in the circuit of the second winding beyond the current source, switch means to connect said resistance in circuit so that with one connection an adjustable portion of the space current to said other tubes can be shunted around said bias winding, and with another connection current from said current source can be shunted through said winding in excess of the space current required by said other tubes.

6. In combination a signal repeater and a polar relay to be operated thereby, said relay having two windings, a sourceof energizing current for said repeater, said repeater embodying means for dividing the energizing current flowing from said source into two components, means in the repeater for varying the flow in one component in accordance with the actual signal pulse received, means for maintaining the flow in the other of said components substantially steady, said dividing means comprising circuits each embodying a controlling resistance having similar ohmic values for widely varying potentials imposed thereupon, means for passing the varied current components through one winding 01' said relay and means for passing the steady current component through the other winding thereof.

7. In combination, a signal repeater and a polar relay to be operated thereby, said relay having two windings, a source of operating current ior said repeater, said repeater embodying a pair of circuit means including a controlling resistance means having similar ohmic values for widely varying potentials imposed thereupon tor dividing the operating current flowing from said source into two substantially equal components, repeater means embodied in the circuit over-which one component flows for varying this component both in accordance with the actual signal pulses and in accordance with the average intensity of said pulses, and filter means in the circuit over which the other component flows for eliminating the signal pulsesand varying the-latter component only in accordance with the average intensity of said pulses, and means for passing one component of current through one winding of said relay in a predetermined direction and means for passing the other component oi current through the other winding of the relay in the opposite direction so that the flux in one winding is opposite and substantially equal to the average flux in the, other winding.

ANTHONY P. J. BOUDREAU. 

